• error (15/15) Feb 11 2017 I'm making a serializer that has a variadic write method that
• rikki cattermole (5/20) Feb 11 2017 Try:
• error (6/10) Feb 11 2017 Perfect! Thanks so much - I wish that hint was in the
• Michael Coulombe (22/33) Feb 11 2017 Do you have a complete code example that gives your error? I
• error (8/29) Feb 12 2017 Oh... That's really strange; I've updated my code to use non

error <error n.com> writes:

I'm making a serializer that has a variadic write method that 
takes arbitrary params
and serializes them;  I want to do the same thing with a read 
method ( pass in your
params by ref, and it populates them with data ) -  however, I 
run into a compiler
error - "cannot be ref" in the foreach statement...  Anyone know 
a workaround for this?  Is this a bug, or by design?

Simplified example:

void populateVars(T...)(T vars){
   // Generates "cannot be ref" compiler error:
   foreach(ref v; vars){
     // Populate v with some data here...
   }
}

rikki cattermole <rikki cattermole.co.nz> writes:

On 12/02/2017 3:41 AM, error wrote:
 I'm making a serializer that has a variadic write method that takes
 arbitrary params
 and serializes them;  I want to do the same thing with a read method (
 pass in your
 params by ref, and it populates them with data ) -  however, I run into
 a compiler
 error - "cannot be ref" in the foreach statement...  Anyone know a
 workaround for this?  Is this a bug, or by design?

 Simplified example:

 void populateVars(T...)(T vars){
   // Generates "cannot be ref" compiler error:
   foreach(ref v; vars){
     // Populate v with some data here...
   }
 }

Try:

foreach(i, v; vars) {
	vars[i] = ...;
}

error <error n.com> writes:

On Saturday, 11 February 2017 at 14:43:18 UTC, rikki cattermole 
wrote:
 Try:

 foreach(i, v; vars) {
 	vars[i] = ...;
 }

Perfect! Thanks so much - I wish that hint was in the 
documentation for variadic functions, although I guess it 
suggests an inefficiency in the compiler - since there would be 
an additional copy of vars[i] created in v.

Michael Coulombe <kirsybuu gmail.com> writes:

On Saturday, 11 February 2017 at 15:02:11 UTC, error wrote:
 On Saturday, 11 February 2017 at 14:43:18 UTC, rikki cattermole 
 wrote:
 Try:

 foreach(i, v; vars) {
 	vars[i] = ...;
 }

 Perfect! Thanks so much - I wish that hint was in the 
 documentation for variadic functions, although I guess it 
 suggests an inefficiency in the compiler - since there would be 
 an additional copy of vars[i] created in v.

Do you have a complete code example that gives your error? I 
can't reproduce it (DMD v2.073.0):

int foo(T...)(T vars) {
     int i = 0;
     foreach(ref v ; vars) {
         v = 5;
         i += v;
     }
     return i;
}
void bar(T...)(ref T vars) {
     foreach(ref v ; vars) {
         v = 3;
     }
}
void main() {
     import std.stdio;
     int x = 7;
     bar(x);
     writeln(foo(4,x,8.2)); // 15, no errors
}

error <error n.com> writes:

On Sunday, 12 February 2017 at 03:34:19 UTC, Michael Coulombe 
wrote:

 Do you have a complete code example that gives your error? I 
 can't reproduce it (DMD v2.073.0):

 int foo(T...)(T vars) {
     int i = 0;
     foreach(ref v ; vars) {
         v = 5;
         i += v;
     }
     return i;
 }
 void bar(T...)(ref T vars) {
     foreach(ref v ; vars) {
         v = 3;
     }
 }
 void main() {
     import std.stdio;
     int x = 7;
     bar(x);
     writeln(foo(4,x,8.2)); // 15, no errors
 }

Oh... That's really strange;  I've updated my code to use non 
indexed foreach, and it's now building without the error...  I 
have absolutely no idea what caused the error to occur.  I've 
also tried reverting to earlier versions of the project, and I 
can't recreate the issue.  If it occurs again, I'll snapshot the 
project and try to make a repeatable set up.